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The intracellular calcium antagonist, TMB-8, inhibits prolactin gene expression in GH3 cells
1Department of Anatomy, University of Connecticut Health Center, Farmington 06032.
Abstract:
We examined the effects of the drug, TMB-8, which promotes sequestration of intracellular Ca2+, on the ability of extracellular Ca2+ to stimulate prolactin gene expression in GH3 cells. TMB-8 inhibited prolactin mRNA levels in a dose-dependent manner in the concentration range of 2.5-10 microM. Prolactin mRNA levels were increased about 18-fold by the addition of 0.1 mM CaCl2, and about 25-fold by the addition of 0.4 mM CaCl2. Addition of 10 microM TMB-8 reduced these levels to about 4-fold and 7-fold, respectively. At 10 microM TMB-8 did not effect total protein synthesis or the Ca2+-induced aggregation of the cells, indicating a selective inhibition by the drug of prolactin gene expression. Both TMB-8 and the calmodulin inhibitor, calmidazolium, reversed the effects of Ca2+ on prolactin mRNA levels in cells that had been pretreated for 2 days with 0.4 mM CaCl2.
Insights
The drug TMB-8 selectively inhibits prolactin gene expression by blocking calcium signaling in GH3 cells. This finding offers insights into calcium
Area of Science:
- Endocrinology
- Molecular Biology
- Cell Biology
Background:
- Extracellular calcium (Ca2+) plays a crucial role in regulating gene expression in pituitary cells.
- Prolactin gene expression is known to be influenced by intracellular calcium levels.
- GH3 cells are a commonly used model for studying pituitary hormone regulation.
Purpose of the Study:
- To investigate the effects of TMB-8, a drug that sequesters intracellular Ca2+, on extracellular Ca2+-stimulated prolactin gene expression in GH3 cells.
- To determine if TMB-8 selectively inhibits prolactin gene expression.
- To explore the role of calcium signaling in prolactin gene regulation.
Main Methods:
- GH3 cells were treated with varying concentrations of TMB-8 and extracellular CaCl2.
- Prolactin mRNA levels were quantified using established molecular biology techniques.
- Total protein synthesis and Ca2+-induced cell aggregation were assessed to evaluate drug specificity.
- Calmodulin inhibitor calmidazolium was used for comparative analysis.
Main Results:
- TMB-8 inhibited prolactin mRNA levels in a dose-dependent manner (2.5-10 microM).
- Extracellular CaCl2 significantly increased prolactin mRNA levels (18-25 fold), an effect reduced by TMB-8 (to 4-7 fold).
- TMB-8 (10 microM) did not affect total protein synthesis or Ca2+-induced cell aggregation, indicating selective inhibition of prolactin gene expression.
- Both TMB-8 and calmidazolium reversed Ca2+ effects on prolactin mRNA in pretreated cells.
Conclusions:
- TMB-8 selectively inhibits prolactin gene expression in GH3 cells by interfering with calcium-mediated signaling pathways.
- The findings highlight the critical role of intracellular calcium sequestration in regulating prolactin gene expression.
- TMB-8 serves as a valuable tool for dissecting the molecular mechanisms underlying calcium-dependent gene regulation in endocrine cells.